Recent display devices have been progressing in terms of displaying images with enhanced resolution, and there is a trend of an increased number of signal lines on a substrate of such recent display devices compared with display devices of the related art. In a display device where a semiconductor chip for a driver is mounted on a substrate, lead lines for leading signal lines out to connection terminals connected to the semiconductor chip are provided in a peripheral region surrounding a display region. Further, in the recent display devices, it is desired that the peripheral region (also referred to as picture-frame region) be reduced in width (namely, the picture-frame region be narrowed). However, because the number of lead lines increases with an increase in the number of signal lines, a large space may be required to arrange the lead lines, which may result in an increased area of the picture-frame region.
Patent Literature 1 described below discloses a display device that includes first gate lead lines, second gate lead lines, and third gate lead lines. In the display device described in Patent Literature 1, the first gate lead lines are formed on a base substrate, the second gate lead lines are formed on a gate insulating layer, and the third gate lead lines are formed on a first passivation film.